ELISA method was used to detect seed-born rate of SMV to sowing the plots which have different primary infection sources. The trap plants indexing daily infection rate and the green-pantraps monitoring alate aphids landing on soybeans were used to study SMV epidemiology. The results indicated the infection rate of SMV was determined by the number of virus acquisition aphids alighting on soybeans. The infection rate resulted from coordination between disease incidence and the number of aphids taking off and ...